The streak tubes have been used heretofore as devices that convert a temporal intensity distribution of light to be measured, into a spatial intensity distribution on an output screen (cf. Patent Literatures 1 and 2 below). A conventional typical streak tube, as shown in FIGS. 8 and 9, has a configuration wherein inside a vacuum airtight container 902 with an entrance window 902a on one end face and an output window 902b on the other end face there are a mesh electrode 903, a focusing electrode 904, an aperture electrode 905, and a sweep electrode 906 arranged along the tube axis in the order named between the entrance window 902a and the output window 902b. A photocathode 907 is disposed on the container-interior-wall-surface side of the entrance window 902a and, a phosphor screen 908 on the container-interior-wall-surface side of the output window 902b. 
The mesh electrode 903 has a structure in which a meshed electrode, for example, at the pitch of 1000 meshes/inch is provided at an end of a cylindrical electrode on the photocathode 907 side. The focusing electrode 904 is an axially symmetric cylindrical electrode. The aperture electrode 905 has a structure in which a circular disk having an aperture, for example, with the diameter of several mm is provided at an end of a short cylindrical electrode on the output window 902b side. The sweep electrode 906 is composed of two deflection plates arranged in symmetry with respect to the tube axis. A negative voltage, for example, of −3 kV is applied to the photocathode 907. A positive voltage, for example, of +3 kV is applied to the mesh electrode 903. A high voltage of positive polarity adjusted so as to optimally focus an electron beam on the phosphor screen 908 is applied to the focusing electrode 904. The ground potential (0 V) is applied to the aperture electrode 905 and the phosphor screen 908.
Light is guided from an external device to the streak tube of this configuration to project a linear optical image A through the entrance window 902a onto the photocathode 907 so as to pass through the center of the photocathode 907. The optical image A is projected so as to make an angle of about 45° with the meshes of the mesh electrode 903 and be in parallel with the deflection plates of the sweep electrode 906, in order to avoid appearance of moiré pattern. Then, the photocathode 907 emits an electron beam in a linear distribution along a direction perpendicular to a normal to the photocathode 907, corresponding to the optical image A. The linear electron beam is accelerated by the mesh electrode 903 and thereafter focused by an axially symmetric electron lens formed by a cylindrical electrode system composed of the mesh electrode 903, the focusing electrode 904, and the aperture electrode 905, to pass through the aperture electrode 905, travel through a gap between the deflection plates of the sweep electrode 906, and then impinge on the phosphor screen 908. As a consequence of this operation, a linear optical image B is generated from the output window 902b. On that occasion, in the duration in which the linear electron beam passes between the two deflection plates of the sweep electrode 906, slant sweep voltages varying with time are applied to those deflection plates. This operation results in sweeping the linear electron beam perpendicularly to its line direction and forming an array of linear optical images B arranged in order in the sweep direction on the phosphor screen 908, so as to form so-called streak images. Namely, a luminance distribution corresponding to a temporal change of intensity of the light to be measured is obtained in the sweep direction on the phosphor screen 908. When this is taken by a TV camera and processed by signal processing, we can obtain a temporal intensity profile of the light to be measured.
The linear electron beam is also focused in the direction perpendicular to the sweep direction on the phosphor screen 908 by the axially symmetric electron lens. Therefore, when optical images of multiple channels are arranged in the line direction of the linear optical image A on the photocathode 907, linear optical images B are formed corresponding to the multiple channels on the phosphor screen 908. By sweeping these optical images of multiple channels, we can acquire data of temporal intensity changes about multiple beams of light at the same time and, for example, we can acquire a time-resolved optical spectrum with input of output light from a spectroscope (multi-channel measurement).